This invention relates to a liquid crystal display device, more particularly to a liquid crystal display device wherein a fill port for inserting a liquid crystal composition is sealed by using a special photo-setting resin composition.
As sealing mediums for sealing the fill port, there have been proposed photo-setting resins such as acrylic or methacrylic resins because of easiness in working operations and lesser deterioration of liquid crystal materials during the sealing operation of the fill port. Curing of such photo-setting resins is greatly influenced by the kinds and amounts of photosensitizers used together with them. For example, if there is used as the sealing medium for the fill port a photosensitive resin composition which requires a longer reaction time for curing, since the contact time with the liquid crystal materials under uncured conditions becomes longer, ionic substances in the resin migrate to and contaminate the liquid crystal materials, which results in lowering operation properties of the resulting liquid crystal display device. Further, since liquid crystal materials are easily deteriorated by exposure to ultraviolet light, longer reaction time makes the deterioration of liquid crystal materials greater. On the other hand, if a large amount of photosensitizer is used in order to shorten the reaction time, ionic substances in the resin are dissolved in the liquid crystal materials by the action of radicals generated from the photosensitizer, which results in lowering impedance of the liquid crystal materials and undesirably increasing consuming current of the resulting liquid crystal display device.
Photosensitizers can be divided into two groups, a radical generating type which generates radicals by decomposition by light and a hydrogen withdrawing type which generates radicals by a hydrogen withdrawing reaction. When a radical generating type photosensitizer is used, the curing reaction rate is generally fast but there is a defect in that the surface of the resin is difficult to be cured and remains sticky due to a reaction between the radicals generated and the oxygen in air. If a large amount of one kind of photosensitizer is used in order to increase the reaction rate, the resulting cured resin becomes brittle. On the other hand, when a hydrogen withdrawing type photosensitizer is used, the reaction on the surface of the resin is not retarded, but the hydrogen withdrawing type photosensitizer is generally slow in the reaction rate.
Therefore, although many photosensitizers are known in this art (e.g. Japanese Patent Appln Kokai (Laid-Open) No. 153651/79), there is scarcely known effective photosensitizers which can cure photo-setting resins uniformly both on the surface and inner portions of the sealed portion of the fill port in a very short time by exposure to light.